Meta-analysis of dropout rates in randomized controlled clinical trials: opioid analgesia for osteoarthritis pain.

BackgroundThe interpretation of opioid studies in patients with chronic pain due to osteoarthritis is limited by a high dropout rate. Therefore, the implication of dropouts on the recommendation of opioids in chronic osteoarthritis pain was analyzed.Data sourcesThe databases of Medline, Embase, the Cochrane Library, and the Internet from 1990–2009 were searched.Study selectionTwo independent authors included randomized controlled clinical trials investigating the effects of chronic opioid treatment for the management of osteoarthritis pain. In order to calculate the odds ratio, only placebo-controlled trials were included.Data extractionThe primary outcome parameter was the dropout rate. Secondarily, the effect size was calculated. Data extraction was conducted by two independent authors.ResultsA total of 19 studies reporting results of 3,871 treatment and 2,080 placebo outcomes were retrieved. Compared to placebo, opioid treatment was associated with a significantly increased total dropout rate (OR=1.3, 95%CI 1.2–1.4). Discontinuation of treatment was related to adverse events (OR=4.0, 95%CI 3.4–4.6). Lack of analgesia was associated with a significantly reduced dropout rate in opioid groups (OR=0.4, 95%CI 0.3–0.5). Analgesic effects were significantly better in opioid-treated patients (p=0.01).ConclusionIn spite of analgesic effects, many osteoarthritis patients prefer to stop chronic opioid use, because of adverse events. Therefore, opioids are not generally recommended in osteoarthritis.